Components having micromechanical sensor elements are in many cases used, particularly in the automotive sector, for detecting various physical quantities (pressure, temperature, air mass, acceleration, revolution speed). Typically, measuring elements on membranes arranged above a cavity are often used for this. For the production of the membrane and the cavity, apart from so-called surface micromachining, in which stacks of layers made up of sacrificial layers and functional layers are deposited, patterned and selectively removed, so-called bulk micromachining is also known, in which structures are worked from solid material. More recent methods combine surface micromachining and bulk micromachining.
For example, International Published Patent Application No. 02/02458, or German Published Patent Application No. 100 32 579, describes a method in which regions of differing porosity are formed in a substrate to produce a hollow space beneath a membrane.
It is known from German Published Patent Application No. 100 30 352 to support a membrane above a cavity using stabilizing elements. Such stabilizing elements may be produced, for example, by a trench etching process as described in the non-prior-published German Patent Nos. 102004036035 and 10358859.
Another possibility for forming a hollow space in a substrate is shown in German Published Patent Application No. 101 14 036. In the method described in that document, first an opening is produced in the substrate, followed by temperature treatment of the substrate. By selection of the temperature and the duration of that annealing process, a hollow space is formed deep inside the substrate, with the opening being closed. By using a plurality of adjacent openings, a membrane with a hollow space beneath it may be produced by that method.
European Published Patent Application No. 1 043 770 describes a method for the production of a cavity, in which first at least one trench is produced in a substrate by a first etching step. After passivation of the walls of the trench, the cavity is formed in the course of a second anisotropic etching step. Enlargement of the cavity may be carried out in a third etching step, which is also anisotropic, by removing the walls between a plurality of adjacent trenches.